Field of the Invention
The present invention relates to a power amplifier module.
Description of Related Art
In a mobile communication apparatus such as a mobile phone, a power amplifier circuit (power-amp) is used to amplify power of a signal to be transmitted to a base station. In recent years, mobile phones have employed modulation methods such as high speed uplink packet access (HSUPA), long-term evolution (LTE), and LTE advanced which are high-speed data communication standards. In such communication standards, in order to improve a communication rate, it is important to reduce a distortion in phase or amplitude. That is, high linearity is required for a power amplifier circuit. In such communication standards, in order to improve the communication rate, a range (dynamic range) in which the amplitude of a signal varies may be broadened. When the dynamic range is broad, a high source voltage is required for enhancing linearity and thus there is a tendency that power consumption in the power amplifier circuit increases.
On the other hand, in mobile phones, a decrease in power consumption is required for extending an available time for calling or communication. For example, Patent Document 1 discloses a linear signal transmitter employing an envelope tracking system which can achieve enhancement of power efficiency by controlling a source voltage of a power amplifier circuit depending on an amplitude level of an input modulation signal.